A lot of the things I know and really use I learned informally. For example, I recently had a craving for sweets. Not just a desire for sweets, but an actual craving where my body said GIVE ME SWEETS. This confused me, since it's not as if the body generally needs sugar. A craving for eggs or fruits or leafy greens makes sense, but why crave sweets? So, I looked up some info online, searched around, and found reasons why the body might crave sweets and how to react in a healthy way. I have a lot of knowledge acquired this way with similar motivations or just curiosity. Which means, I have a fair bit of practical knowledge I can actually use. Certainly more than I learned in my health classes.

I don't think I'd want to use unschooling myself, but I think people underestimate how much of what people learn and use is learned informally.